A Risk based inspection methodology for the geothermal power plant piping (Research case: Meshginshahr geothermal power plant)

In Meshginshahr geothermal power plant, fluid with high temperature and pressure comes out of the NWS6D well and are divided into two phases of water and steam by the condenser of the wellhead and by two pipelines (loop1 carrying steam and loop2 carrying water) is transferred to the power plant and the electricity is generated. Risk-based technical inspection technique has never been used in the piping systems of geothermal power plants. In this paper, the implementation of risk-based inspection methodology in geothermal power plants is presented. To perform the risk-based inspection technique in the loops, first the corrosion mechanisms are identified and by specifying the corrosion mechanisms, the probability and consequence of failure of each mechanism and consequently the risk of corrosion in each loop are determined. Experiments using Potentiodynamic polarization test are employed to investigate the general corrosion rate of the pipe materials. According to the studies conducted in this article, in loop 1, the risk of corrosion of carbon dioxide and pitting corrosion is moderate and the risk of corrosion of sour water is low and the risk of loop 2 in case of pitting corrosion is high while in the case of sulfuric acid corrosion, it shows a low amount.